Dehydrogenation catalyst containing platinum rhenium germanium and an alkali or alkaline earth metal

ABSTRACT

DEHYDROGENATABLE HYDROCARBONS ARE DEHYDROGENATED BY CONTACTING THEM AT DEHYDROGENATION CONDITIONS WITH A CATALYTIC COMPOSITE COMPRISING A COMBINATION OF CATALYTICALLY EFFECTIVE AMOUNTS OF PLATINUM GROUP COMPONENT, A RHENIUM COMPONENT, A GERMANIUM COMPONENT AND AN ALKALI OR ALKALINE EARTH METAL WITH A POROUS CARRIER MATERIAL. A SPECIFIC EXAMPLE OF THE CATALYTIC COMPOSITE DISCLOSED HEREIN IS A COMBINATION OF A PLATINUM COMPONENT, A RHENIUM COMPONENT, A GERMANIUM COMPONENT AND AN ALKALI OR ALKALINE EARTH COMPONENT WITH AN ALUMINA CARRIER MATERIAL, WHEREIN THE COMPONENTS ARE PRESENT IN AMOUNTS SUFFICIENT TO RESULT IN THE COMPOSITE CONTAINING, ON AN ELEMENTAL BASIS, 0.01 TO 2 WT. PERCENT PLATINUM, 0.01 TO 2 WT. PERCENT RHENIUM, 0.01 TO 5 WT. PERCENT GERMANIUM AND 0.1 TO 5 WT. PERCENT OF ALKALI OR ALKALINE EARTH METAL.

United States Patent O U.S. Cl. 252-466 PT 13 Claims ABSTRACT OF THEDISCLOSURE Dehydrogenatable hydrocarbons are dehydrogenated bycontacting them at dehydrogenation conditions with a catalytic compositecomprising a combination of catalytically effective amounts of aplatinum group component, a rhenium component, a germanium component andan alkali or alkaline earth metal with a porous carrier material. Aspecific example of the catalytic composite disclosed herein is acombination of a platinum component, a rhenium component, a germaniumcomponent and an alkali or alkaline earth component with an aluminacarrier material, wherein the components are present in amountssufi'lcient to result in the composite containing, on an elementalbasis, 0.01 to 2 Wt. percent platinum, 0.01 to 2 wt. percent rhenium,0.01 to wt. percent germanium and 0.1 to 5 wt. percent of alkali oralkaline earth metal.

CROSS REFERENCES TO RELATED APPLICATIONS This application is acontinuation-in-part of my prior application entitled HydrocarbonConversion Process and Catalyst Therefor, filed July 3, 1969 andassigned Ser. No. 839,086.

DISCLOSURE The subject of the present invention is broadly an improvedmethod for dehydrogenating a dehydrogenatable hydrocarbon to produce aproduct containing the same number of carbon atoms but fewer hydrogenatoms. In another aspect, the present invention includes a method ofdehydrogenating normal parafiin hydrocarbons containing 4 to 30 carbonatoms per molecule to the corresponding normal mono-olefins with minimumproduction of side products. Yet another aspect of the present inventioninvolves a novel catalytic composite comprising a combination ofcatalytically effective amounts of a platinum group component, a rheniumcomponent, a germanium component, and an alkali or alkaline earthcomponent with a porous carrier material, which composite has highlypreferred characteristics of activity, selectivity, and stability whenit is employed in the dehydrogenation of dehydrogenatable hydrocarbonssuch as aliphatic hydrocarbons, naphthenic hydrocarbons andalkylaromatic hydrocarbons.

The dehydrogenation of dehydrogenatable hydrocarbons is an importantcommercial process because of the great and expanding demand fordehydrogenated hydrocarbons for use in the manufacture of variouschemical products such as detergents, plastics, synthetic rubbers,pharmaceutical products, high octane gasoline, perfumes, drying oils,ion-exchange resins, and various other products well known to thoseskilled in the art. One example of this demand is in the manufacture ofhigh octane gasoline by using C and C mono-olefins to alkylateisobutane. Another example of this demand is in the area ofdehydrogenation of normal paraffin hydrocarbons to produce normalmono-olefins having 4 to 30 carbon atoms per molecule. These normalmono-olefins can, in turn, be

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utilized in the synthesis of vast numbers of other chemical products.For example, derivatives of normal mono-olefins have become ofsubstantial importance to the detergent industry where they are utilizedto alkylate an alkylatable aromatic such as benzene, with subsequenttransformation of the product arylalkane into a wide variety ofbiodegradable detergents such as the alkylaryl sulfonate type ofdetergent Which is most widely used today for household, industrial, andcommercial purposes. Still another large class of detergents producedfrom these normal mono-olefins are the oxyalkylated phenol derivativesin which the alkyl phenol base is prepared by the alkylation of phenolwith these normal mono-olefins. Still another type of detergent producedfrom these normal monoolefins is a biodegradable alkylsulfate formed bythe di rect sulfation of the normal mono-olefin. Likewise, the olefincan be subjected to direct sulfonation with sodium bis-ulfite to makebiodegradable alkylsulfonates. As a further example, these mono-olefinscan be hydrated to produce alcohols which then, in turn, can be used toproduce plasticizers and/ or synthetic lube oils.

Regarding the use of products made by the dehydrogenation ofalkylaromatic hydrocarbons, these find Wide application in industriesincluding the petroleum, petrochemical, pharmaceutical, detergent,plastic industries, and the like. For example, ethylbenzene isdehydrogenated to produce styrene which is utilized in the manufactureof polystyrene plastics, styrene-butadiene rubber, and the likeproducts. Isopropylbenzene is dehydrogenated to form alpha-methylstyrene which, in turn, is extensively used in polymer formation and inthe manufacture of drying oils, ion-exchange resins, and the likematerial.

Responsive to this demand for these dehydrogenation products, the arthas developed a number of alternative methods to produce them incommercial quantities. One method that is widely utilized involves theselective dehydrogenation of dehydrogenatable hydrocarbons by contactingthe hydrocarbons with a suitable catalyst at dehydrogenation conditions.As is the case with most catalytic procedures, the principal measure ofeffectiveness for this dehydrogenation method involves the ability toperform its intended function with minimum interference of sidereactions for extended periods of time. The analytical terms used in theart to broadly measure how well a particular catalyst performs itsintended functions in a particular hydrocarbon conversion reaction areactivity, selectivity, and stability, and for purposes of discussionhere these terms are generally defined for a given reactant as follows:(1) activity is a measure of the catalysts ability to convert thehydrocarbon reactant into products at a specified severity level whereseverity level means the conditions usedthat is, the temperature,pressure, con tact time; and presence of diluents such as H (2)selectivity usually refers to the amount of desired product or productsobtained relative to the amount of the reactant converted; (3) stabilityrefers to the rate of change with time of the activity and selectivityparameters-obviously the smaller rate implying the more stable catalyst.More specifically, in a dehydrogenation process, activity commonlyrefers to the amount of conversion that takes place for a givendehydrogenatable hydrocarbon at a specified severity level and istypically measured on the basis of disappearance of the dehydrogenatablehydrocarbon; selectivity is typically measured by the amount, calculatedon a mole percent of converted dehydrogenatable hydrocarbon basis, ofthe desired dehydrogenated hydrocarbon obtained at the particularseverity level; and stability is typically equated to the rate of changewith time of activity as measured by disappearance of thedehydrogenatable hydrocarbon and of selectivity as measured by theamount of desired hydrocarbon produced. Accordingly,

the major problem facing workers in the hydrocarbon dehydrogenation artis the development of a more active and selective catalytic compositethat has good stability characteristics.

I have now found a catalytic composite which possesses improvedactivity, selectivity, and stability when it is employed in a processfor the dehydrogenation of dehydrogenatable hydrocarbons. In particular,I have determined that a combination of catalytically effective amountsof a. platinum group component, a rhenium component, a germaniumcomponent, and an alkali or alkaline earth component with a porous,refractory carrier material enables the performance of a dehydragenationprocess to be substantially improved. Moreover, particularly goodresults are obtained when this composite is utilized in thedehydrogenation of long chain normal paraffins to produce thecorresponding normal mono-olefins with minimization of side reactionssuch as skeletal isomerization, aromati- Zation and cracking.

It is accordingly one object of the present invention to provide a novelmethod for dehydrogenation of dehydrogenatable hydrocarbons utilizing acatalytic composite containing a platinum group component, a rheniumcomponent, a germanium component, or an alkali or alkaline earthcomponent combined with a porous carrier material. A second object is toprovide a novel catalytic composite having superior performancecharacteristics when utilized in a dehydrogenation process. Anotherobject is to provide an improved method for the dehydrogenation ofnormal parafiin hydrogen to produce normal mono-olefins. Yet anotherobject is to improve the performance of a platinum-containingdehydrogenation catalyst by using a combination of a relativelyinexpensive component, germanium, and a relatively expensive component,rhenium, to beneficially interact with the platinum met-a1.

In brief summary, one embodiment of the present invention involves amethod for dehydrogenating a dehydrogenatable hydrocarbon whichcomprises contacting the hydrocarbon at dehydrogenation conditions witha catalytic composite comprising a combination of a platinum groupcomponent, a rhenium component, a germanium component, and an alkali oralkaline earth component with a porous carrier material. The catalyticcomposite contains these components in amounts, calculated on anelemental basis, of about 0.01 to about 2 wt. percent of the platinumgroup metal, about 0.01 to about 2 wt. percent rhenium, about 0.01 toabout 5 wt. percent germanium, and about 0.1 to about 5 wt. percent ofthe alkali or alkaline earth metal.

A second embodiment relates to the dehydrogenation method describedabove wherein the dehydrogenatable hydrocarbon is an aliphatic compoundcontaining 2 to 30 carbon atoms per molecule.

A third embodiment relates to a novel catalytic com posite containing acombination of a platimum group component, a rhenium component, agermanium component and an alkali or alkaline earth component with aporous carrier material. These components are present in this compositein amounts sufiicient to result in the composite containing, on anelemental basis, about 0.01 to about 2 wt. percent of platinum groupmetal, about 0.01 to about 2 wt. percent rhenium, 0.01 to about 5 wt.percent germanium, and about 0.1 to about 5 wt. percent of the alkali oralkaline earth metal.

Other objects and embodiments of the present invention concern specificdetails regarding essential and preferred catalytic ingredients,preferred amounts of components in the composite, suitable methods ofcomposite preparation, suitable dehydrogenatable hydrocarbons, operatingconditions for use in the dehydrogenation process, and the likeparticulars. These are hereinafter given in the following detaileddiscussion of each of these facets of the present invention.

Regarding the dehydrogenatable hydrocarbon that is subjected to theinstant method, it can, in general, be an organic compound having 2 to30 carbon atoms per molecule and containing at least 1 pair of adjacentcarbon atoms having hydrogen attached thereto. That is, it is intendedto include within the scope of the present invention the dehydrogenationof any organic compound capable of being dehydrogenated to produceproducts containing the same number of carbon atoms but fewer hydrogenatoms, and capable of being vaporized at the dehydrogenation conditionsused herein. More particularly, suitable dehydrogenatable hydrocarbonsare: aliphatic compounds containing 2 to 30 carbon atoms per molecule,alkylaromatic hydrocarbons where the alkyl group contains 2 to 6 carbonatoms, and naphthenes or alkyd-substituted naphthenes. Specific examplesof suitable dehydrogenatable hydrocarbons are: (1) alkanes such asethane, propane, n-butane, isobutanes, n-pentane, isopentane,neopentane, n-hexane, Z-methylpentane, 2,2-dimethylbutane, n-heptane,Z-methylhexane, 2,2,3-trimethylbutane, and the like compounds; (2)naphthenes such as cyclopentane, methylcyclopentane, ethylcyclopentane,n-propylcyclopentane, cyclohexane, isopropylcyclopentane, 1,3-dimethylcyclohexane, and the like compounds; and, (3) alkylaromaticssuch as ethylbenzene, n-propylbenzene, n-butylbenzene,1,3,5-triethylbenzene, isopropylbenzene, isobutylbenzene,ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon is a normalparaffin hydrocarbon having about 4 to about 30 carbon atoms permolecule. For example, normal paraffin hydrocarbons containing about 10to 15 carbon atoms per molecule are dehydrogenated by the subject methodto produce the corresponding normal mono-olefin which can, in turn, bealkylated with benzene and sulfonated to make alkylbenzene sulfonatedetergents having superior biodegradability. Likewise, n-alkanes having12 to 18 carbon atoms per molecule can be dehydrogenated to thecorresponding normal mono-olefin which, in turn, can be sulfated orsulfonated to make excellent detergents. Similarly, n-alkanes having 6to 10 carbon atoms per molecule can be dehydrogeuated to form thecorresponding mono-olefins which can, in turn, be by drated to producevaluable alcohols. Preferred feed streams for the manufacture ofdetergent intermediates contain a mixture of 4 or 5 adjacent normalparafiin homlogues such as C to C C to C C to C and the like mixtures.

An essential feature of the present invention involves the use of acatalytic composite comprising a combination of catalytically effectiveamounts of a platinum group component, a rhenium component, a germaniumcomponent, and an alkali or alkaline earth component with a porouscarrier material.

Considering first the porous carrier material, it is preferred that thematerial be a porous, adsorptive, high surface area support having asurface area of about 25 to about 500 m. gm. The porous carrier materialshould be relatively refractory to the conditions utilized in thedehydrogenation process, and it is intended to include Within the scopeof the present invention carrier materials which have traditionally beenutilized in hydrocarbon conversion catalysts such as: (1) activatedcarbon, coke, or charcoal; (2) silica or silica gel, silicon carbide,clays, and silicates including those synthetically prepared andnaturally occurring, which may or may not be acid treated for example,attapulgus clay, china clay, diatomaceous earth, fullers earth, kaolin,kieselguhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria, silicazirconia, etc.; (5) crystalline aluminosilicates such as naturallyoccurring or synthetically prepared mordenite and/or faujasite either inthe hydrogen form or in a form which has been treated with multivalentcations; and, (6) combinations of one or more elements from thesegroups. The preferred porous carrier materials are refractory inorganicoxides, with best results obtained with an alumina carrier material.Suitable alumina materials are the crystalline aluminas known as thegamma-, eta, and theta-alumina, with gammaor etaalumina giving bestresults. In addition, in some embodiments the alumina carrier materialmay contain minor proportions of other well known refractory inorganicoxides such as silica, zirconia, magnesia, etc.; however, the preferredsupport is substantially pure gammaor etaalumina. Preferred carriermaterials have an apparent bulk density of about 0.3 to about 0.7gm./cc. and surface area characteristics such that the average porediameter is about to 3000 angstroms, the pore volume is about 0.1 toabout 1 ml./gm. and the surface area is about 100 to about 500 m. gm. Ingeneral, best results are typically obtained with a gamma-aluminacarrier material which is used in the form of spherical particleshaving: a relatively small diameter (i.e., typically about y inch), anapparent "bulk density of about 0.5 gm./cc., a pore volume of about 0.4ml./gm., and a surface area of about 175 m. gm.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or naturally occurring.Whatever type of alumina is employed it may be activated prior to use byone or more treatments including drying, calcination, steaming, etc.,and it may he in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide to a solution of a salt of aluminum such as aluminumchloride, aluminum nitrate, etc., in an amount to form an aluminumhydroxide gel which upon drying and calcining is converted to alumina.The alumina carrier may be formed in any desired shape such as spheres,pills, cakes, extrudates, powders, granules, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere; and alumina spheres may becontinuously manufactured by the well known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid combining the resulting hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300 F. toabout 400 F. and subjected to a calcination procedure at a temperatureof about 850 F. to about 1300 F. for a period of about 1 to about 20hours. It is also a good practice to subject the calcined particles to ahigh temperature steam treatment in order to remove as much as possibleof undesired acidic components. This manufacturing procedure effectsconversion of the alumina hydrogel to the corresponding crystallrnegamma-alumina. See the teachings of U.S. Pat. No. 2,620,- 314 foradditional details.

One essential constituent of the catalyst of the present invention is agermanium component. This component may be present in the composite asan elemental metal or as a chemical compound such as the correspondingoxide, sulfide, oxychloride, halide, etc., and it may be utilized in anyamount which is catalytically effective. Best results are, in general,obtained when this component is present in an oxidation state above thatof the elemental metal; for example, as germanium dioxide. In addition,it is preferred to have the germanium component uniformly distributedthroughout the carrier material. Preferably this component is used in anamount sufficient to result in the final catalytic composite containing,on an elemental basis, 0.01 to about 5 wt. percent germanium, with bestresults typically obtained with about 0:05 to about 2 wt. percentgermanium. This component may be incorporated in the catalytic compositein any suitable manner such as by coprecipitation 0r cogellation withthe porous carrier material, ion-exchange with the carrier material orimpregnation of the carrier material at any step in the preparation. Itis understood that it is intended to include Within the scope of thepresent invention all conventional methods for incorporating a metalliccomponent in a catalytic composite, and the particular method ofincorporation used is not deemed to be an essential feature of thepresent invention. One acceptable method of incorporating the germaniumcomponent into the catalytic composite involves coprecipitating orcogelling the germanium component during the preparation of thepreferred carrier material, alumina. This method typically involves theaddition of a suitable soluble, decomposable germanium compound, such asgermanium tetrachloride, to the aluminum hydrosol. Then the resultingmixture of the germanium compound and hydrosol is combined with asuitable gelling agent and dropped into an oil bath, etc., as explainedin detail hereinbefore. After drying and calcining the resulting gelledcarrier material there is obtained an intimate combination of aluminaand germanium oxide. A preferred method of incorporating the germaniumcomponent involves utilization of a soluble, decomposable compound ofgermanium to impregante the porous carrier material. The solvent used inthis impregnation step is generally selected on the basis of thecapability to dissolve the selected germanium compound; typically, it isan aqueous, acidic solution. Thus, the germanium component may be addedto the carrier material by commingling the latter With an aqueous,acidic solution of a suitable germanium salt or compound of germaniumsuch as germanium tetrachloride, germanium difiuoride, germaniumdioxide, germanium tetrafiuoride, germanium di-iodide, germaniummonosulfide and the like compounds. A particularly preferredimpregnation solution comprises germanium metal dissolved in chlorinewater. In general, the germanium component can be impregnated eitherprior to, simultaneously with, or after the platinum group and rheniumcomponents are added to the carrier material. However, I have foundexcellent results when the germanium component is impregnatedsimultaneously with the platinum group and rhenium components. In fact,one preferred impregnation solution contains chloroplatinic acid,perrhenic acid, nitric acid, and germanium metal dissolved in chlorinewater.

A second essential constituent for the catalytic composite used in thepresent invention is a platinum group component. Although the process ofthe present invention is specifically directed to the use of a catalyticcomposite containing platinum, it is intended to include other platinumgroup metals such as palladium, rhodium, ruthenium, osmium, and iridium.The platinum group component, such as platinum, may exist within thefinal catalytic composite as a compound such as the oxide, sulfide,halide, etc., or as an elemental metal. Generally, the amount of theplatinum group component present in the final catalyst is small comparedto the quantities of the other components combined therewith. In fact,the platinum group metallic component generally comprises about 0.01 toabout 2% by Weight of the final catalytic composite, calculated on anelemental basis. Excellent results are obtained when the catalystcontains about 0.05 to about 1 wt. percent of the platinum group metal.The preferred platinum group component is platinum or a compound ofplatinum, although good results are obtained when it is palladium or acompound of palladium.

The platinum group component may be incorporated in the catalyticcomposite in any suitable manner such as coprecipitation or cogellationwith the carrier material, ion-exchange with the carrier material and/orhydrogel, or impregnation either after or before calcination of thecarrier material, etc. The preferred method of preparing the catalystinvolves the utilization of a soluble, decomposable compound of theplatinum group metal to impregnate the porous carrier material. Forexample, the platinum group metal may be added to the carrier bycommingling the latter with an aqueous solution of chloroplatinic acid.Other water-soluble compounds of the platinum group metals may beemployed in impregnation solutions and include ammonium chloroplatinate,bromoplatinic acid, platinum chloride, dinitrodiaminoplatinum, palladiumchloride, palladium nitrate, palladium sulfate, diamine palladiumhydroxide, tetraminepalladium chloride, etc. The utilization of aplatinum chloride compound such as chloroplatinic acid is ordinarilypreferred. In addition, it is generally preferred to impregnate thecarrier material after it has been calcined in order to minimize therisk of washing away the valuable platinum metal compounds; however, insome cases it may be advantageous to impregnate the carrier when it isin a gelled state.

Another essential ingredient of the catalyst of the present invention isthe rhenium component. This component may be present as an elementalmetal, as a chemical compound such as oxide, sulfide, halide, etc., oras a physical or chemical combination with the porous carrier materialand/ or other components of the catalytic composite. The rheniumcomponent is preferably utilized in an amount sufficient to result in afinal catalytic composite containing about 0.01 to about 2 wt. percentrhenium,

calculated on an elemental basis, with best results obtained at a levelof about 0.05 to about 1 wt. percent. The rhenium component maybeincorporated in the catalytic composite in any suitable manner and atany stage in the preparation of the catalyst. It is generally advisableto incorporate the rhenium component in an impregnation step after theporous carrier material has been formed in order that the expensivemetal will not be lost due to Washing and purification treatments whichmay be applied to the carrier material during the course of itsproduction. Although any suitable method for incorporating a catalyticcomponent in a porous carrier material can be utilized to incorporatethe rhenium component, the preferred procedure involves impregnation ofthe porous carrier material. The impregnation solution can, in generalbe a solution of a suitable soluble, decomposable rhenium salt such asammonium perrhenate, sodium perrhenate, potassium perrhenate, and thelike salts. In addition, solutions of rhenium halides such as rheniumchloride, may be used; the preferred impregnation solution is, however,an aqueous solution of perrhenic acid. The porous carrier material canbe impregnated with the rhenium component either prior to,simultaneously with, or after the other components mentioned herein arecombined therewith. Best results are ordinarily achieved when therhenium component is impregnated simultaneously with the other metalliccomponents. In fact, excellent results are obtained with a one stepimpregnation procedure utilizing as an impregnation solution, an aqueoussolution of chloroplatinic acid, perrhenic acid, nitric acid, andgermanium metal dissolved in chlorine water.

Yet another essential ingredient of the catalyst used in the presentinvention is the alkali or alkaline earth component. More specifically,this component is selected from the group consisting of the compounds ofthe alkali metalscesium, rubidium, potassium, sodium, and lithium--andof the alkaline earth metalscalcium, strontium, barium, and magnesium.This component may exist Within the catalytic composite as a relativelystable compound such as the oxide or sulfide, or in combination with oneor more of the other components of the composite, or in combination withthe carrier material such as, for example, in the form of a metalaluminate. Since, as is explained hereinafter, the composite containingthe alkali or alkaline earth is always calcined in an air atmospherebefore use in the conversion of hydrocarbons, the most likely state thiscomponent exists in during use in dehydrogenation is the metallic oxide.Regardless of what precise form in which it exists in the composite, theamount of this component utilized is preferably selected to provide acomposite containing about 0.1 to about 5 wt. percent of the alkali oralkaline earth metal, and, more preferably, about 0.25 to about 3.5 wt.percent. Best results are obtained when this component is a compound oflithium or potassium.

This alkali or alkaline earth component may be combined with the porouscarrier material in any manner known to those skilled in the art such asby impregnation, coprecipitation, physical mixture, ion-exchange and thelike procedures. However, the preferred procedure involves impregnationof the carrier material either before, during or after it is calcined,or before, during or after the other materials are added to the carriermaterial. Best results are ordinarily obtained when this component isadded to the carrier material after the other metallic componentsbecause the alkali metal or alkaline earth metal acts to neutralize someof the acid used in the preferred impregnation procedure for thesemetallic components. In fact, it is preferred to add the platinum group,rhenium and germanium components to the carrier material, 0X- idize theresulting composite in an air stream at a high temperature (i.e.,typically about 600 to 1000 F.), then treat the resulting oxidizedcomposite with a mixture of air and steam in order to remove residualacidity and thereafter add the alkali metal or alkaline earth component.Typically, the impregnation of the carrier material with this componentis performed by contacting the carrier material with a solution of asuitable decomposable compound or salt of the desired alkali or alkalineearth metal. Hence, suitable compounds include the alkali metal oralkaline earth metal halides, sulfates, nitrates, acetates, carbonates,phosphates and the like compounds. For example, excellent results areobtained by impregnating the carrier material after the platinum group,rhenium and germanium components have been combined therewith, with anaqueous solution of lithium nitrate or potassium nitrate. Following theaddition of this component, the resulting composite is dried andcalcined in an air stream as is subsequently discussed.

Regarding the preferred amounts of the various metallic components ofthe subject catalyst, I have found it to be a good practice to specifythe amounts of the germanium, the rhenium and the alkali or alkalineearth components as a function of the amount of the platinum groupcomponent. On this basis, the amount of the germanium component isordinarily selected so that the atomic ratio of the germanium metal tothe platinum group metal contained in the composite is about 0.25:1 toabout 6:1. Likewise, the amount of the rhenium component is selected toresult in an atomic ratio of rhenium to platinum group metal of about0.121 to about 3:1. Similarly, the amount of the alkali or alkalineearth component is ordinarily selected to produce a composite containingan atomic ratio of alkali or alkaline earth metal to the platinum groupmetal of about 5:1 to about 50:1 or more, with the preferred range beingabout 10:1 to about 25:1.

Another significant parameter for the subject catalyst is the totalmetals content which is defined to be the sum of the platinum groupcomponent, the rhenium component, the germanium component, and alkali oralkaline earth component, calculated on an elemental metal basis. Goodresults are ordinarily obtained with the subject catalyst when thisparameter is fixed at a value of from 0.13 to about 14 wt. percent, with:best results ordinarily achieved at a metals loading of about 0.5 toabout 6.5 wt. percent.

Integrating the above discussion of each of the essential components ofthe catalytic composite used in the present invention, it is evidentthat a particularly preferred catalytic composite comprises acombination of a platinum component, a rhenium component, a germaniumcomponent and an alkali or alkaline earth component with an aluminacarrier material in amounts sufiicient to result in the compositecontaining from about 0.05 to about 1 wt. percent platinum, about 0.05to about 1 wt. percent rhenium, about 0.05 to about 2 wt. percentgermanium, and about 0.25 to about 3.5 Wt. percent of the alkali oralkaline earth metal. Accordingly, specific examples of especiallypreferred catalytic composites are as follows: 1) a catalytic compositecomprising 0.375 wt. percent platinum, 0.2 wt. percent rhenium, 0.25 wt.percent germanium, and 0.5 wt. percent lithium combined with an aluminacarrier material; (2) a catalytic composite comprising 0.375 wt. percentplatinum, 0.1 wt. percent rhenium, 0.5 wt. percent germanium, and 2.8wt. percent potassium combined with an alumina carrier material; and (3)a catalytic composite comprising 0.375 wt. percent platinum, 0.375 wt.percent rhenium, 0.375 wt. percent germanium and 0.5 wt. percent lithiumcombined with an alumina carrier material.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the resulting compositegenerally will be dried at a temperature of about 200 F. to about 600 F.for a period of from about 2 to 24 hours or more, and finally calcinedat a temperature of about 600 F. to about 1100 F. in an air atmospherefor a period of about 0.5 to 10 hours, preferably about 1 to abouthours, in order to substantially convert the metallic components to theoxide form. When acidic components are present in any of the reagentsused to eifect incorporation of any one of the components of the subjectcomposite, it is a good practice to subject the resulting composite to ahigh temperature treatment with steam or with a mixture of steam andair, either after or before the calcination step described above, inorder to remove as much as possible of the undesired acidic component.For example, when the platinum group component is incorporated byimpregnating the carrier material with chloroplatinic acid, it ispreferred to subject the resulting composite to a high temperaturetreatment with steam in order to remove as much as possible of theundesired chloride.

It is preferred that the resultant calcined catalytic composite besubjected to a substantially water-free reduction prior to its use inthe conversion of hydrocarbons. This step is designed to insure auniform and finely divided dispersion of the metallic componentsthroughout the carrier material. Preferably, substantially pure and dryhydrogen (i.e., less than 20 vol. p.p.m. H O) is used as the reducingagent in this step. The reducing agent is contacted with the calcinedcomposite at a temperature of about 800 F. to about 1200 F., a gashourly space velocity of about 100 to about 5,000 hr. and for a periodof time of about 0.5 to hours or more, effective to substantially reduceat least the platinum group component. This reduction treatment may beperformed in situ as part of a start-up sequence if precautions aretaken to predry the plant to a substantially water-free state and ifsubstantially water-free hydrogen is used.

Although it is not essential, the resulting reduced catalytic compositemay, in some cases, be beneficially subjected to a presulfidingoperation designed to incorparte in the catalytic composite from about0.05 to about 0.50 wt. percent sulfur calculated on an elemental basis.Preferably, this presulfiding treatment takes place in the presence ofhydrogen and a suitable sulfur-containing compound such as hydrogensulfide, lower molecular weight mercaptans, organic sulfides, etc.Typically, this procedure comprises treating the reduced catalyst with asulfiding gas such as a mixture containing a mole ratio of H to H 5 ofabout 10:1 at conditions sufiicient to effect the desired incorporationof sulfur, generally including a temperature ranging from about 50 F. upto about 1100 F. or more. This presulfiding step can be performed insitu or ex situ.

According to the method of the present invention, the dehydrogenatablehydrocarbon is contacted with a cata- 10 lytic composite of the typedescribed above in a dehydrogenation zone at dehydrogenation conditions.This contacting may be accomplished by using the catalyst in a fixed bedsystem, a moving bed system, a fluidized bed system, or in a batch typeoperation; however, in view of the danger of attrition losses of thevaluable catalyst and of well known operational advantages, it ispreferred to use a fixed bed system. In this system, the hydrocarbonfeed stream is preheated by any suitable heating means to the desiredreaction temperature and then passed into a dehydrogenation zonecontaining a fixed bed of the catalyst type previously characterized. Itis, of course, understood that the dehydrogenation zone may be one ormore separate reactors with suitable heating means therebetween toinsure that the desired conversion temperature is maintained at theentrance to each reactor. It is also to be noted that the reactants maybe contacted with the catalyst bed in either upward, downward, or radialflow fashion, with the latter being preferred. In addition, it is to benoted that the reactants may be in the liquid phase, a mixedliquid-vapor phase, or a vapor phase when they contact the catalyst,with best results obtained in the vapor phase.

Although hydrogen is the preferred diluent for use in the subjectdehydrogenation method, in some cases other art-recognized diluents maybe advantageously utilized such as steam, methane, carbon dioxide, andthe like diluents. Hydrogen is preferred because it serves thedualfunction of not only lowering the partial pressure of thedehydrogenatable hydrocarbon, but also of suppressing the formation ofhydrogen-deficient, carbonaceous deposits on the catalytic composite.Ordinarily, hydrogen is utilized in amounts sufficient to insure ahydrogen to hydrocarbon mole ratio of about 1:1 to about :1, with bestresults obtained in the range of about 1.5:1 to about 10:1. The hydrogenstream charged to the dehydrogenation zone will typically be recyclehydrogen obtained from the efiluent stream from this zone after asuitable separation step.

Concerning the conditions utilized in the process of the presentinvention, these are generally selected from the conditions well knownto those skilled in the art for the particular dehydrogenatablehydrocarbon which is charged to the process. More specifically, suitableconversion temperatures are selected from the range of about 700 toabout 1200 F., with a value being selected from the lower portion ofthis range for the more easily dehydrogenated hydrocarbons such as thelong chain normal parafiins and from the higher portion of this rangefor the more diflicultly dehydrogenated hydrocarbons such as propane,butane, and the like hydrocarbons. For example, for the dehydrogenationof C to Can normal paraffins, best results are ordinarily obtained at atemperature of about 800 to about 950 F. The pressure utilized isordinarily selected at a value which is as low as possible consistentwith the maintenance of catalyst stability, and is usually about 0.1 toabout 10 atmospheres, with best results ordinarily obtained in the rangeof about .5 to about 3 atmospheres. In addition, a liquid hourly spacevelocity (calculated on the basis of the volume amount, as a liquid, ofhydrocarbon charged to the dehydrogenation zone per hour divided by thevolume of the catalyst bed utilized) is selected from the range of about1 to about 40 hrr with best results for the dehydrogenation of longchain normal parafiins typically obtained at a relatively high spacevelocity of about to hrf Regardless of the details concerning theoperation of the dehydrogenation step, an efiluent stream will bewithdrawn therefrom. This effluent will contain unconverteddehydrogenatable hydrocarbons, hydrogen, and products of thedehydrogenation reaction. This stream is typically cooled and passed toa separating zone wherein a hydrogen-rich vapor phase is allowed toseparate from a hydrocarbon-rich liquid phase. In general, it is usuallydesired to recover the unreacted dehydrogenatable hydrocarbon from thishydrocarbon-rich liquid phase in order to make the dehydrogenationprocess economically attractive. This recovery step can be accomplishedin any suitable manner known to the art such as by passing thehydrocarbon-rich liquid phase through a bed of suitable adsorbentmaterial which has the capability to selectively retain thedehydrogenated hydrocarbons contained therein or by contacting same witha solvent having a high selectivity for the dehydrogenated hydrocarbonor by a suitable fractionation scheme where feasible. In the case wherethe dehydrogenated hydrocarbon is a mono-olefin, suitable adsorbentshaving this capability are activated silica gel, activated carbon,activated alumina, various types of specially prepared molecular sieves,and the like adsorbents. In another typical case, the dehydrogenatedhydrocarbons can be separated from the unconverted dehydrogenatablehydrocarbons by utilizing the inherent capability of the dehydrogenatedhydrocarbons to enter into several well known chemical reactions such asalkylation, oligomerization, halogenation, sulfonation, hydration,oxidation, and the like reactions. Irrespective of how thedehydrogenated hydrocarbons are separated from the unreactedhydrocarbons, a stream containing the unreacted dehydrogenatablehydrocarbons will typically be recovered from this hydrocarbonseparation step and recycled to the dehydrogenation step. Likewise, thehydrogen phase present in the hydrogen separating zone will be withdrawntherefrom, a portion of it vented from the system in order to remove thenet hydrogen make, and the remaining portion is typically recycled,through suitable compressing means, to the dehydrogenation step in orderto provide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chainnormal parafiin hydrocarbons are dehydrogenated to the correspondingnormal mono-olefins, a preferred mode of operation of this hydrocarbonseparation step involves an alkylation reaction. In this mode, thehydrocarbon rich liquid phase withdrawn from the separating zone iscombined with a stream containing an alkylatable aromatic and theresulting mixture passed to an alkylation zone containing a suitablehighly acidic catalyst such as an anhydrous solution of hydrogenfluoride. In the alkylation zone the mono-olefins react with thealkylatable aromatic while the unconverted normal parafiins remainsubstantially unchanged. The efi luent stream from the alkylation zonecan then be easily separated, typically by means of a suitablefractionation system, to allow recovery of the unreacted normalparafiins. The resulting stream of unconverted normal parafiins is thenusually recycled to the dehydrogenation step of the present invention.

The following working examples are introduced to illustrate further thenovelty, mode of operation, utility, and benefits associated with thedehydrogenation method and catalytic composite of the present invention.These examples are intended to be illustrative rather than restrictive.

These examples are all performed in a laboratory scale dehydrogenationplant comprising a reactor, a hydrogen separating zone, a heating means,cooling means, pumping means, compressing means, and the like equipment.In this plant, the feedstrearn containing the dehydrogenatablehydrocarbon is combined with a hydrogen stream and the resultant mixtureheated to the desired conversion temperature, which refers herein to thetemperature maintained at the inlet to the reactor. The heated mixtureis then passed into contact with the catalyst which is maintained as afixed bed of catalyst particles in the reactor. The pressures reportedherein are recorded at the outlet from the reactor. An efiluent streamis withdrawn from the reactor, cooled, and passed into the separatingzone wherein a hydrogen gas phase separates from a hydrocarbon-richliquid phase containing dehydrogenated hydrocarbons, unconverteddehydrogenatable hydrocarbons and a minor amount of side products of thedehydrogenation reaction. A portion of the hydrogen-rich gas phase isrecovered as excess recycle gas with the remaining portion beingcontinuously recycled through suitable compressive means to the heatingzone as described above. The hydrocarbon-rich liquid phase from theseparating zone is withdrawn therefrom and subjected to analysis todetermine conversion and selectivity for the desired dehydrogenatedhydrocarbon as will be indicated in the examples. Conversion numbers ofthe dehydrogenatable hydrocarbon reported herein are all calculated onthe basis of disappearance of the dehydrogenatable hydrocarbon and areexpressed in mole percent. Similarly, selectivity numbers are reportedon the basis of moles of desired hydrocarbon produced per moles ofdehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are prepared accordingto the following general method with suitable modifications instoichiometry to achieve the compositions reported in each example.First, an alumina carrier material comprising A inch spheres is preparedby: forming an aluminum hydroxyl chloride sol by dissolvingsubstantially pure aluminum pellets in a hydrochloric acid solution,adding hexamethylenetetramine to the sol, gelling the resulting solutionby dropping it into an oil bath to form spherical particles of analumina hydrogen, aging, and washing the resulting particles with anammoniacal solution and finally drying, calcining, and steaming the agedand washed particles to form spherical particles of gamma-aluminacontaining substantially less than 0.1 wt. percent combined chloride.Additional details as to this method of preparing this alumina carriermaterial are given in the teachings of U.S. Pat. No. 2,620,314.

Second, a measured amount of germanium dioxide powder is placed in aporcelain boat and subjected to a reduction treatment with substantiallypure hydrogen at a temperature of about 650 C. for about 2 hours. Theresulting grayish-black solid material is dissolved in chlorine water toform a solution. An aqueous solution containing chloroplatinic acid,perrhenic acid and nitric acid is also prepared. The two solutions arethen intimately admixed and used to impregnate the gamma-aluminaparticles. The amounts of the various reagents are carefully selected toyield final catalytic composites containing the required amounts ofplatinum, rhenium and germanium. In order to insure uniform distributionof metallic components throughout the carrier material, thisimpregnation step is performed by adding the alumina particles to theimpregnation mixture with constant agitation. The impregnation mixtureis maintained in contact with the alumina particles for a period ofabout /2 hour at a temperature of 70 F. thereafter, the temperature ofthe impregnation mixture is raised to about 225 F. and the excesssolution is evaporated in a period of about one hour. The resultingdried particles are then subjected to a calcination treatment in an airatmosphere at a temperature of about 500 to about 1000 F. for about 2 to10 hours. Thereafter, the resulting calcined particles are treated withan air stream containing from about 10 to about 30% steam at atemperature of about 800 to about 1ODO F. for an additional period fromabout 1 to about 5 hours in order to further reduce the residualcombined chloride in the composite.

Finally, the alkali or alkaline earth metal component is added to theresulting calcined particles in a second impregnating step. This secondimpregnation step involves contacting the calcined particles with anaqueous solution of a suitable decomposable salt of the desired alkalior alkaline earth component. For the composites utilized in the presentexamples, the salt is either lithium nitrate or potassium nitrate. Theamount of this salt is carefully chosen to result in a final compositehaving the desired composition. The resulting alkali impregnatedparticles are then dried, calcined and steamed in exactly the samemanner as described above following the first impregnation step.

In all the examples the catalyst is reduced during startup by contactingwith hydrogen at an elevated temperature and thereafter sulfided with amixture of H and H 8.

13 EXAMPLE I The reactor is loaded with 100 cc. of a catalystcontaining, on an elemental basis, 0.375 wt. percent platinum, 0.2 wt.percent rhenium, 0.25 wt. percent germanium, 0.5 wt. percent lithium andless than 0.15 wt. percent chloride. The feed stream utilized iscommercial grade isobutane containing 99.7 wt. percent isobutane and 0.3wt. percent normal butane. The feed stream is contacted with thecatalyst at a temperature of 1065 F., a pressure of p.s.i.g., a liquidhourly space velocity of 4.0 hr.- and a hydrogen to hydrocarbon moleratio of 2:1. The dehydrogenation plant is lined-out at these conditionsand a 20 hour test period commenced. The hydrocarbon product stream fromthe plant is continuously analyzed by GLC (gas-liquid chromatography)and a high conversion of isobutane is observed with a selectivity forisobutylene of at least 80%.

EXAMPLE II The catalyst contains, on an elemental basis, 0.375 wt.percent platinum, 0.5 wt. percent germanium, 0.1 wt. percent rhenium,0.5 wt. percent lithium, and less than 0.15 wt. percent combinedchloride. The feed stream is commercial grade normal dodecane. Thedehydrogenation reactor is operated at a temperature of 870 F., apressure of 10 p.s.i.g., a liquid hourly space velocity of 32 hr. and ahydrogen to hydrocarbon mole ratio of 8:1. After a line-out period, a 20hour test period is performed during which the average conversion of thenormal dodecane is maintained at a high level with a selectivity fornormal dodecene of about 90%.

EXAMPLE III The catalyst is the same as utilized in Example II. The feedstream is normal tetradecane. The conditions utilized are a temperatureof 840 F., a pressure of 20 p.s.i.g., a liquid hourly space velocity of32 hr.- and a hydrogen to hydrocarbon mole ratio of 8:1. After aline-out period, a 20 hour test shows an average conversion ofapproximately 12% and a selectivity for normal tetradecane of above 90%.

EXAMPLE IV The catalyst contains, on an elemental basis, 0.2 wt. percentplatinum, 0.2 wt. percent rhenium, 0.5 wt. percent germanium and 0.6 wt.percent lithium, with combined chloride being less than 0.2 wt. percent.The feed stream is substantially pure normal butane. The conditionsutilized are a temperature of 950 F., a pressure of 15 p.s.i.g., aliquid hourly space velocity of 4.0 hrr and a hydrogen to hydrocarbonmole ratio of 4:1. After a line-out period, a hour test is performed andexcellent conversion of the normal butane to normal butene is observed.

EXAMPLE V The catalyst contains, on an elemental basis, 0.375 wt.percent platinum, 0.375 wt. percent rhenium, 0.5 wt. percent germanium,2.8 wt. percent potassium, and less than 0.2 wt. percent combinedchloride. The feed stream is commercial grade ethylbenzene. Theconditions utilized are a pressure of 15 p.s.i.g., a liquid hourly spacevelocity or" 32 hr. a temperature of 1050" R, and a hydrogen tohydrocarbon mole ratio of 8:1. During a 20 hour test period, at least85% of equilibrium conversion of the ethylbenzene is observed.

It is intended to cover by the following claims all changes andmodifications of the above disclosure of the present invention thatwould be self-evident to a man of ordinary skill in the catalystformulation art or in the hydrocarbon dehydrogenation art.

I claim as my invention:

1. A catalytic composite comprising a combination of a platinum groupcomponent, a rhenium component, a germanium component and an alkali oralkaline earth component with a porous carrier component in amountssufiicient to result in a composite containing, on an elemental basis,about 0.01 to about 2 wt. percent platinum group metal, about 0.01 toabout 2 wt. percent rhenium, about 0.01 to about 5 Wt. percentgermanium, and about 0.1 to about 5 wt. percent of alkali or alkalineearth metal, said germanium component being present in an oxidationstate above that of the elemental metal.

2. A catalytic composite as defined in claim 1 wherein said platinumgroup component is platinum or a compound of platinum.

3. A catalytic composite as defined in claim 1 wherein said platinumgroup component is palladium or a compound of palladium.

4. A catalytic composite as defined in claim 1 wherein said porouscarrier material is a refractory inorganic oxide.

5. A catalytic composite as defined in claim 4 wherein said refractoryinorganic oxide is alumina.

6. A catalytic composite as defined inclaim 1 wherein said alkali oralkaline earth component is a compound of lithium.

7. A catalytic composite as defined in claim 1 wherein said alkali oralkaline earth component is a compound of potassium.

8. A catalytic composite as defined in claim 1 wherein the atomic ratioof rhenium to platinum group metal contained in the composite is about0.1:1 to about 3:1, wherein the atomic ratio of germanium to platinumgroup metal contained in the component is about 0.25:1 to about 6:1 andwherein the atomic ratio of alkali or alkaline earth metal to platinumgroup metal is about 5:1 to about 5021.

9. A catalytic composite comprising a combination of a platinumcomponent, a rhenium component, a genmanium component and an alkali oralkaline earth component with an alumina carrier material in amountssutficient to result in a composite containing, on an elemental basis,about 0.01 to about 2 wt. percent platinum group metal, about 0.01 toabout 2 wt. percent rhenium about 0.01 to about 5 wt. percent germanium,and about 0.1 to about 5 wt. percent of alkali or alkaline earth metal,said germanium component being present in an oxidation state above thatof the elemental metal.

10. A catalytic composite as defined in claim 9 wherein said compositecontains, on an elemental basis, about 0.05 to about 1 wt. percentplatinum, about 0.05 to about 1 wt. percent rhenium, about 0.05 to about2 wt. percent germanium, and about 0.25 to about 3.5 wt. percent of thealkali or alkaline earth metal.

11. A catalytic composite as defined in claim 9 wherein said alkali oralkaline earth component is a compound of lithium.

12. A catalytic composite as defined in claim 9 wherein said alkali oralkaline earth metal is a compound of potassium.

13. A catalytic composite as defined in claim 9 wherein the atomic ratioof rhenium to platinum contained in the composite is about 0.01 to about321, wherein the atomic rate of germanium to platinum contained in thecomposite is 0.25:1 to about 6: 1, and wherein the atomic ratio ofalkali or alkaline earth metal to platinum is about 5:1 to about 50:1.

References Cited UNITED STATES PATENTS 2,906,700 9/1959 Stine et al.252466 PT X 3,315,007 4/1967 Abell et al. 252466 PT X 3,434,960 3/1969Jacobson et al. 252466 PT 3,470,262 9/ 1969 Michaels et a1. 260680CURTIS R. DAVIS, Primary Examiner US. 01. X.R. 252461, 475,476; 260-668,669; 683.3

